Design of the advanced regional aircraft, the DART-75

This design analysis is intended to show the capabilities of the DART-75, a 75 passenger medium-range regional transport. Included are the detailed descriptions of the structures, performance, stability and control, weight and balance, and engine design. The design should allow for the DART to become the premier regional aircraft of the future due to some advanced features like the canard, semi-composite construction, and advanced engines

Forage fish interactions: A symposium on creating the tools for ecosystem-based management of marine resources

Forage fish (FF) have a unique position within marine foodwebs and the development of sustainable harvest strategies for FF will be a critical step in advancing and implementing the broader, ecosystem-based management of marine systems. In all, 70 scientists from 16 nations gathered for a symposium on 12–14 November 2012 that was designed to address three key questions regarding the effective management of FF and their ecosystems: (i) how do environmental factors and predator–prey interactions drive the productivity and distribution of FF stocks across ecosystems worldwide, (ii) what are the economic and ecological costs and benefits of different FF management strategies, and (iii) do commonalities exist across ecosystems in terms of the effective management of FF exploitation

Are we ready to track climate-driven shifts in marine species across international boundaries? - A global survey of scientific bottom trawl data

Marine biota are redistributing at a rapid pace in response to climate change and shifting seascapes. While changes in fish populations and community structure threaten the sustainability of fisheries, our capacity to adapt by tracking and projecting marine species remains a challenge due to data discontinuities in biological observations, lack of data availability, and mismatch between data and real species distributions. To assess the extent of this challenge, we review the global status and accessibility of ongoing scientific bottom trawl surveys. In total, we gathered metadata for 283,925 samples from 95 surveys conducted regularly from 2001 to 2019. We identified that 59% of the metadata collected are not publicly available, highlighting that the availability of data is the most important challenge to assess species redistributions under global climate change. Given that the primary purpose of surveys is to provide independent data to inform stock assessment of commercially important populations, we further highlight that single surveys do not cover the full range of the main commercial demersal fish species. An average of 18 surveys is needed to cover at least 50% of species ranges, demonstrating the importance of combining multiple surveys to evaluate species range shifts. We assess the potential for combining surveys to track transboundary species redistributions and show that differences in sampling schemes and inconsistency in sampling can be overcome with spatio-temporal modeling to follow species density redistributions. In light of our global assessment, we establish a framework for improving the management and conservation of transboundary and migrating marine demersal species. We provide directions to improve data availability and encourage countries to share survey data, to assess species vulnerabilities, and to support management adaptation in a time of climate-driven ocean changes.En prensa6,86

Assessing the Control of Preservational Environment on Taphonomic and Ecological Patterns in an Oligocene Mammal Fauna from Badlands National Park, South Dakota

Comparisons of paleofaunas from different facies are often hampered by the uncertainty in the variation of taphonomic processes biasing the paleoecological parameters of interest. By examining the taphonomic patterns exhibited by different facies in the same stratigraphic interval and area, it is possible to quantify this variation, and assess inter-facies comparability. The fossil assemblages preserved in Badlands National Park (BNP), South Dakota, have long been a rich source for mammalian faunas of the White River Group. To investigate the influence of the variation of taphonomic bias with lithology whilst controlling for the influence of changes in patterns of taphonomic modification with time, taphonomic and paleoecological data were collected from four mammal-dominated fossil assemblages (two siltstone hosted and two sandstone hosted) from a narrow stratigraphic interval within the Oligocene Poleslide Member of the Brule Formation, in the Palmer Creek Unit of BNP. Previous work in the region confirmed that the two major lithologies represent primarily aeolian- and primarily fluvial-dominated depositional environments, respectively. A suite of quantifiable taphonomic and ecological variables was recorded for each of the more than 800 vertebrate specimens studied here (857 specimens were studied in the field, 9 specimens were collected and are reposited at BNP). Distinctly different patterns of taphonomic biasing were observed between the aeolian and fluvial samples, albeit with some variability between all four sites. Fluvial samples were more heavily weathered and abraded, but also contained fewer large taxa and fewer tooth-bearing elements. No quantifiable paleofaunal differences in generic richness or evenness were observed between the respective facies. This suggests that while large vertebrate taxonomic composition in the region did vary with paleodepositional environment, there is no evidence of confounding variation in faunal structure, and therefore differences between the assemblages are attributed to differing preservational environments producing a taphonomic overprint on the assemblages. The lack of apparent taphonomic bias on paleofaunal structure suggests that such paleoecological data can be compared throughout the Poleslide Member, irrespective of lithology